Overload relay switch with ambient temperature compensation



Oct. 13, 1959 H; Eo SCHLEICHER 2,908,786

OVERLOAD-RELAY SWITCH WITH AMBIENT TEMPERATURE COMPENSATION Filed Jan.4, 1957 A INVENToR. F/ 6 5 HfO/dESm/@fc/ye/ BY h/s afforneys www.

United States Patent Ciice OVERLOAD RELAY SWITCH WITH AMBIENTTEMPERATURE CMPENSATION Harold E. Schleicher, West Hartford, Conn.,assignor to The Arrow-Hart & Hegeman Electric Company, Hartford, Conn.,a corporation of Connecticut Application January 4, 1957, Serial No.632,460 12 Claims. (Cl. 200-116) This invention relates to switchmechanism. More particularly, it relates to a snap switch mechanism ofthe type in my prior Patent 2,322,161 of June 15, 1943, which isparticularly useful as a relay in controlling electromagneticcontactors, as may be seen by reference to said patent. The mechanism ofthe relay disclosed therein is operable in response to overloadconditions to automatically move into open-circuit position. It can alsobe set either to automatically reset itself or to require manualresetting from open-circuit position. Only so much of the mechanism aswill be helpful in understanding the present invention will be describedherein.

Although the relay switch as illustrated in my prior patent has provedvery satisfactory in usage over a considerable period, there are timesand conditions where greater accuracy could be achieved if saidmechanism were provided with ambient temperature compensation. Undersome circumstances, the ambient temperature will vary over such limitsas to alter the predetermined setting of the relay and cause the relayto operate at a higher or lower current value than desired.

Therefore, it is an object of the present invention to provide ambienttemperature control means for the overload relay switch of the type inmy prior patent.

Another object is to provide such ambient temperature control withoutalteration in the operating mechanism as a whole or the desirablecharacteristics of operation of the relay in my pn'or patent.

Other objects and advantages of the invention will become apparent as itis described in connection with the accompanying drawing.

Although the invention will be described as applicable to my priorpatent, it will be understood that its principles are not limited inthat respect.

In the drawing:

Fig. 1 is an end elevation view of the invention.

Fig. 2 is a vertical section view along the line 2-2 of Fig. l.

Fig. 3 is a perspective view of the component elements of the ambienttemperature controlling means employed n my invention.

Referring to vthe drawing, the parts are mounted in a base of moldedinsulating material. The base is generally of the same rectangular formand the same configuration as in my prior patent. The base has alongitudinal horizontal dividing wall 12 in the midportion of the baseto separate the switch mechanism from the load responsive elements ofthe device. The switch mechanism is located below the dividing wall andthe load responsive elements, comprising a heater coil 14 and bimetalstrip 16, are located above the dividing wall.

The heater 14 may be in the form of a coiled wire or a strip havingproper characteristics of resistance for the current to be regulated.The ends of the resistance element 14 preferably are secured by screws17 to terminal plates 18 which in turn are screwed to the top of thebase by screws.

The bimetal is shielded from the heater 14 by a ash 2,908,786 PatentedOct. 13, 1959 plate 22 which extends below the heater from one end ofthe base toward the other and is attached at one end to the terminalelement 18.

The bimetal 16 is pivotally and movably mounted at one end as willhereinafter be more fully described. As the bimetal bends upon thegeneration of heat by the heater 14, the free end of the bimetal engagesa roller 40 upon an integral axle 42 which is guided for verticalmovement in the walls of the base. The opposite ends of the roller axle42 are rotatably mounted in a pair of insulating bars 46, only one ofwhich is visible, which are connected at their lower ends by atransverse pin 48 to one end of an operating stamped sheet metal lever50.

As the operating lever moves in a vertical plane about its pivot pin 52,it is biased in clockwise direction by a restoring spring 54 which iswound about the pin 52 and has one end pressing against the lever andthe other against a wall of the casing.

The right end of the lever 50 has a hook formation to receive a loop onone end of the coiled tensioned switch spring 56, the other end of whichis attached to a U- shaped movable contact member 58, near one endthereof. Parallel side arms of the movable contact member are notched attheir free ends to receive coaxial pivot pins 60. On the transverseportion of the contact member is a downwardly facing contact button inposition to engage and disengagc a Contact button 66.

The contact button 66 is mounted on one end of a short piece ofresilient sheet metal 68, the other end of which is secured by a screwto a terminal vplate for the purpose of connection of the relay switchcontact to and outside the terminal.

The amount of upward travel of the movable contact member as it isactuated by the overcenter spring 56 during the movement of the line ofaction of that spring across the axis of the pivot pin 60 is limited bya stop pin which extends transversely of the casing from a verticallyreciprocative resetting plunger 92 and whose position is adjustable asdescribed in my prior patent.

The operation of the structure illustrated herein is similar underoverload conditions to that described in my prior patent. As the bimetalbecomes heated by the excess current passing through the heater 14, thebimetal will bend down until its end presses upon the roller 40 causingthe insulating bars 46 to act on the operating lever 50 to rotate thelever counterclockwise. As the switch spring 56 moves upwardly acrossthe axis of the pivot pin 60 that overcenter movement will cause themovable contact member 58 to move in clockwise direction to causecontact separation. Manual resetting 1s accomplished by pushing down onthe resetting button or plunger 92.

Provision for ambient temperature compensation is made by mounting themain bimetal 16 in a novel fashion. Near one end of that bimetal, theright end as illustrated in Fig. 2, a small bearing plate 81 is ixedlysecured to the bottom surface by riveting or otherwise. A portion 81a ofthe bearing plate is pressed to form a semi-cylindrical bearing or seatfor a pivot pin 82 whose axis is parallel to and extends transverselywith respect to the bimetal 16. The ends of the pin extend beyond thesides of the bimetal and are journalled in an inverted U-shaped stampedsheet metal supporting bracket 83 which is held in a recess in the topof one end of the base 10, by the terminal plate 18.

Parallel to the main bimetal 16 and located at the bottom of the casingin a position where it is accessible by removal of a bottom plate is acompensating strip bimetal 80 which is identical in dimensions andmaterial' itsy right end on a pin in the same way as the main bimetalexcept that its supporting bracket 86 faces oppositely from the mainbimetal supporting bracket and has the endser of its, side arms 86sturned outwardly and screwedzagainst downwardly facingledges inthebottom part of the base 10.

i-E'aclr bimetal has a; iingerllrY and 80x) extending from ritspivotedend. These ngersft snugly in upper and lower; apertures,respectively, in a tie-bar or strip 85 which may conveniently be stampedfrom sheet metal of suiciently heavy gauge to provide a substantiallyrigid bar.l

Inordertoy adjust the position of the compensating bimetal; anadjustment screw or bolt87 is mounted in its free or llexingend. Areduced neck is formed near the end of the adjustment screw which isassembled by lateral slidinginto a slot 88s formed in the. olset. end ofa llexiblev strip 88A of sheet metal which at this other end is heldagainst a downwardly facing ledge in the bottom part of the base by ascrew bolt or in any suitable fashion. This strip 88 is stiff enough sothat upon turning of the adjustment screw 87 the position of thecompensatingbimetal may be varied, but is resilient enough not to bindtheV bimetal. The slot 88s extends in the samedirection as the bimetaltoavoid binding of the adjustment screw and bimetal.

. The resilience of the mounting ofthe adjustment means also avoidsunwanted stress on the compensating bimetall when the main bimetal isheated and is acting to open the switch contacts. During such action,the compensating vbimetal might otherwise on some occasions be caused tomove and be subjected to unwanted stress.

y.From the `foregoing, it will be clear that by manipulating theadjustment screw the compensating bimetal is caused to pivot about itsmounting pin 84 and consequentlywill cause movement of. the tie bar 85which in turn will cause pivoting of the bracket and rnain bimetal Whenthe` parts are arranged as illustrated in the` drawing, the compensatingbimetal will bow inwardly of the casing as the ambient temperaturerises. The main bimetal will bow outwardly on any temperature rise, thuscausing its free end (left) to deflect toward the bottom of the casing.

Since the` end at which the adjustment screw 87 ot the compensatingbimetal is located cannot move closer to the casing during bowing, theopposite end will cause pivoting clockwise of the ngerk 80x, therebymoving the bar 85V down. That will pivot the main bimetal clockwiseabout pivot 82,. The result is to require greater bowingor deflection ofthe main bimetal before tripping the switch` open, as the main bimetalis heated due to excess current in the heater 14.

\ By manipulating the adjustment screw 87 to move the adjustment end ofthe compensating bimetal. inwardly,V

both bimetals move together and the main bimetal can be adjusted to actat the precise current setting desired. However, this'adjustment is aiine adjustment as the main current calibration ofthe device is done bysubstituting heaters l14 of different characteristics, as heretofore.

` Many modifications Within the scope of the invention will occur tothose skilled in the art. Therefore, I do not limit the vinvention tothe specific form and structure described.v n j iWhat is claimed is: j

l. In an electric switch, separable contacts, means to operate Nsaidcontacts including a lirst bimetallic strip one end of which ispositioned to move and cause contact separation, a pivot for said strip,an extension rigid with the `strip on the opposite side of said pivot, astrip of bimetalrfor ambient temperature compensation, apivotalmountingfor said compensating bimetal independent of said,` strippivot, an extension rigid. withsaid compensatilng bimetal onthef..oppositev side ofA said pivotal mount1ng,.a tie bar connectingsaidextensions and causing said rst bimetal to turn upon its pivot as thetemperature of said compensating bimetal rises.

2. In an electric switch, separable contacts, mechanism including anactuating element of which a certain amount of movement operates saidcontacts, a rst bimetallic strip one end of' which is positioned to movesaid actuating element, aV pivot for said strip, an extension -rigidwith the strip on the opposite side of said pivot, a strip of bimetalfor ambient temperature compensation, a pivotal mounting for saidcompensating bimetal, an extension rigid with said compensatingbimetalon the opposite side of -said pivotal mounting, a tie bar connectingsaid extensions vand causing said rst bimetal to urn upon its pivot asthe temperature of said compensating bimetal rises, means to adjust theposition of said compensating bimetal to vary the relation of said firstbimetal to said actuating element.

3. In an electric switch, separable contacts, 'mechanism including` anactuating element of which a certain amount of movement operates saidcontacts, a rst bimetallic strip one end ofy which Yis positionedto movesaid actuating element, Ia pivotforrsaid strip,`an extension rigid withthe strip on the opposite side of said pivot, a strip 'of bimetal forambient temperature compensation,a pivotal mounting for saidcompensating bimetal,y an extension rigid with said `compensatingbimetal on the opposite side of said pivotal mounting, and a tie barhaving linger and slot connections between said extensions and said tie'bar andcausing said rst bimetal to turn upon its pivot as thetemperature of said compensatingbimetal rises.

4. In an electric switch, separable contacts, means to operate saidcontacts including av iirst bimetallic strip one end of which ispositioned `to'niove and cause contactseparation, a pivot for saidstrip, an extension rigid with the rstrip on the opposite side'ot'saidpivot, a strip of bimetal identical with said rst bimetallic strip andmounted parallel thereto-for ambient temperature cornpensation, alpivotal mountingfor. said compensating bimetal similar tothepivotalmounting of said irst bimetal, an extension rigid with said`compensating bimetalsimilar to the extension beyond said'first bimetal,a tie bar connecting said extensions andv causing said first bimetal toturn upon its pivotas the temperature of said compensating bimetalrises. f

5. In an Velectric switch, separablecontacts, mechanism including anactuating element of which a certain amount of movement operates saidcontacts, a rst Ybimetallic striponeend of which is positioned to` movesaid: actuating element, a pivot. for .said strip, .an extension rigidwith the strip on the opposite4 sideV of said pivot, a strip of bimetalfor ambient temperature rcompensation, a pivotalv mountingA for saidcompensating bimetal, an extension rigid with said compensating bimetallonthe opposite side of said pivotal mounting, a tie bar connecting saidextensions and causing said'frstbimetal to-tur-n upon its pivot as thetemperatureofV saidvcompensating bimetal rises, an adjustment boltconnected to a lixedpartA of the switch and engaging with the end ofsaidcompensating bimetal for moving the latter'- about its pivot providingadjustment for it and said firsty bimetal strip. f

6. In an electric switch, separable contacts, mechanism including anactuating elementl of which a certa-in amount of movementv operates saidcontacts, a rst bimetallic strip one end ofwwhich is positioned tomovesaid actuating element, apivotV for saidl strip, an extension rigidwithy thestrip on the opposite side Vof'said pivot, afstrip of bimetalfor ambient'- temperat'ure compensation, a pivotal vmounting forsaid-compensating bimetal, an extension rigid with=said-comp`ensatingbimetal onY the opposite side of said pivotal mounting,I a tiebarconnecting said extensions and causingvsaidijst bimetal to turn-upon itspivot as thetemperature ofsaid-compensating bimetal rises, anadjustmentbolt connected/with a" xed part oill the switch and'-engaging-withftlie end of said? compensating bimetal for moving thelatter about its pivot providing adjustment for it and said rst bimetalstrip, said adjustment bolt having a reduced neck permitting exing ofsaid compensating bimetal without binding or unwanted distortion.

7. A device as claimed in claim 6 wherein said fixed [part to which saidadjustment bolt is connected comprises a flexible member having a slottherein in which said reduced neck is slidably engaged.

8. In an electric switch, separable contacts, means to operate saidcontacts including a first bimetallic strip one end of which ispositioned to move freely and cause contact operation, a pivot for saidstrip spaced from said free end, a strip of bimetal for ambienttemperature compensation, a pivotal mounting for said compensatingbimetal independent of said iirst pivot, means connecting saidbimetallic strips causing them to pivot identical amounts about theirpivots as the temperature of said compensating bimetal rises thereby tocompensate for ambient temperature rise, the connection of saidconnecting means to said first strip being at a point remote from itsfree end so as not to impede the movement of said free end.

9. In an electric switch, separable contacts, means to operate saidcontacts including a rst bimetallic strip one end of which is positionedto move and to cause contact operation, a pivot for said strip spacedfrom said free end, a strip of bimetal for ambient temperaturecompensation having the same characteristics as said first strip, apivotal mounting for said compensating bimetal located in the sameposition along said compensating bimetal as the pivot of said firststrip and independent of said strip pivot, and means connecting saidbimetallic strips causing said first bimetal to turn upon its pivot asthe temperature of said compensating bimetal rises, t0 compensate forambient temperature rise, the connection of said connecting means tosaid first strip being at a point remote from its free end so as not toimpede the movement of said free end.

10. In an electric switch, separable contacts, means to operate saidcontacts including a first bimetallic strip one end of which ispositioned to move and cause contact operation, a pivot for said stripspaced from said free end, a strip of bimetal for ambient temperaturecompensation, a pivotal mounting for said compensating bimetal, saidbimetallic strips being identical in character and in relation of theirpivots thereto, and means causing said first strip to turn upon itspivot in corresponding amount to the compensating strip as thetemperature of said compensating strip rises, the last-mentioned meansbeing connected to said first strip at a point remote from its free endso as not to impede the movement of said free end.

11. An electric switch as claimed in claim 10 in which a rigidconnecting member nonrigidly connects said strips and causes turning ofthe first strip corresponding to the compensating strip on both heatingand cooling of the compensating strip.

l2. An electric switch as claimed in claim 8 in which a rigid connectingmember nonrigidly connects said strips and causes turning of the firststrip corresponding to the compensating strip on both heating andcooling of the compensating strip.

References Cited in the tile of this patent UNITED STATES PATENTS1,784,450 Klahn Dec. 9, 1930 2,041,511 Pearce May 19, 1936 2,171,895Sardeson Sept. 5, 1939 2,235,337 Shaw Mar. 18, 1941 2,392,498 OsterheldIan. 8, 1946 2,416,170 Gano et al. Feb. 18, 1947 2,863,023 Rowe Dec. 2,1958 FOREIGN PATENTS 436,010 Great Britain Oct. 3, 1935

